The experience of a traumatic event induces emotional memories that last a lifetime. Children are particularly vulnerable to traumatic events, a risk factor associated with the development of psychopathology. Little is known about the learning processes in early life that result in long-lasting fear memories. The objective of this application is to develop a novel paradigm to investigate fear memory formation and retention in the infant animal. We hypothesize that our paradigm will prove to be a valid model for the study of long-lasting memories after a severe acute threat in young rats. To test this hypothesis, we use an apparatus in which young rats are exposed to an ecologically relevant threat, a natural predator, the cat. We test four predictions of fear conditioning theory: 1) single exposure to severe threat induces fear memories; 2) fear memories can persist for prolonged periods of time; 3) the intensity of stimulation determines the magnitude of fear memories; 4) young animals form fear memories. Young rats of two different ages, preweaning 14-day-olds and postweaning 26-day-olds, are exposed to the live cat in a single session. Odor of the cat is delivered to the rat in different concentrations in an airflow system. Cat odor of different intensities is paired with a neutral odor in a classical conditioning task. Fear memories to cue and context are assessed 1, 7, 30 and 60 days later. A better understanding of fear memory formation in early development is the critical first step in building a translational model of childhood trauma. [unreadable] [unreadable]